Magnesium is known to dilate cerebral arteries and to block N-methyl-D-aspartate receptors in the injured neurons.

Intravenous magnesium may prevent vasospasm after subarachnoid hemorrhage and may protect neurons against damage during established vasospasm.

The IMASH trial is a randomized, placebo-controlled, double-blinded, multi-center trial to evaluate the effect that intravenous magnesium sulfate infusion on the clinical outcome of patients with aneurysmal subarachnoid haemorrhage.

Methods:

After obtaining randomisation code:

Start MgSO4 20 mmol over 30 minutes, followed by infusion of 80 mmol/day or equivalent volume of saline within 48 h after onset of symptom,

Study drug to be infused for 14 days from the day of hemorrhage (regarded as day 0).

Plasma magnesium concentration in the IV MgSO4 group should be raised to 2.0-2.5 mmol/L or twice the serum baseline level. Patients that are randomized to saline infusion will only have their magnesium levels normalized if there is a clinical indication to do so.